Yep, you just toss a piece of fruit/veggie in their container and they'll eat it if they're hungry.
That does make sense! I honestly debate over this myself, especially when I have perfectly good full grown roaches that die, that I hate to waste. Unfortunately I usually say that unless they've died very recently and are "fresh", it's best not to feed them. As soon as they die their insides start rotting, and if you aren't sure how long it's been it's probably best to be safe and just toss them.